Recovery of tar acids



Lgzasog S. Pf MILLER RECOVERY oF- TAR ACIDS Filed July 16, 1927 Y 2 Shets-Shee l INYENTOR m ATTORNEY Oct. 6, 1931.

s. P. MILLER 1,825,8.09

RECOVERY OF' TAR ACIDS Filed July 16, 1927 v 2 Sheets--Sheet 2 Iv 22 x lb :L :L u lL/Z V 5' 27 www 34, l ATTORNEY:

Patented Oct. 6, 1931 UNITED STATE S PATENT oFFlcE STUART PABMEIEE MILLER, F GLEN NEW JERSEY, ASSIGNOR T0 THE BAB'- BETT COMPANY, OF NEW YORK, N. Y., A CORPORATION 0F NEW JERSEY c tar-acids and ammonia, as well as other prod-v to a regulated temperature,-

oint of water,at which a pitch of low melt-` of the tar-acids willremain in vapor state,`

application mea July 1c;

l This invention relates to the recovery *of ucts, at coal distillation plants, such ascoke oven plants. l 'According to the present invention, thehot coal distillation gases, such as coke oven gases, are subjected tocooling to cool the above the dew ing point will be carried in suspension in the gases and at which a considerable amount then cleaned'to remove a low melting point pitch therefrom, for example, with'- an electrical precipitator, then passed through an ammoniaabsorber or saturator at a temperature above ,the dew point of water and a temperature such that the tar acids will remain largely in the vapor state, then cooled to separate a tar-acid oil therefrom,.and then finally subjected to a scrubbing or absorbing treatment for the recovery of coke oven light oils. The tar-acids are extracted Afrom the tar acid oil.

The present invention is an improvement in direct ammonia processes in which the ammonia is directly absorbed from the hot.

coke oven gases at a temperature above the dew point of water, and combines such direct ammoma recovery wlth thedirect recover `from the gases o a low melting point pitc 'mercial product, for example, for road making or treating purposes. c

According to thel present invention, the coke oven gases are cooled to a regulated temperature, e. g. around 110 to 120 C., and the gases are then subjected to a cleaning treatment for the separation of pitch there- REcovEaY or fran noms 1927. seriarno. ao'zo.y

from. This' cleaning treatment may advantage'ously be ,with an electricalprecipitator, which will `separate from the gases the pitch particles carried in suspension therein, leaving clean gases containing ammonia and tar acld-oils in vaporform. v

By maintaining the gases at a temperature around 110 to 120 C., or somewhat higher, there can 'be directly separated from the gases in the electrical precipitator a pitch of melting point adapting it for use directly for road making or treating surfaces, for example, a pitch having a melting point around 105 F. (or Ll0.5" (1.). The removal of pitch 4'particles from the gases at such temperatures will leave the gases at a temperature considerably above the dew point of water, and the gases will still contain a considerable amount of the tar acid content of the gases in vapor form, together with oil constituents in vapor form. By subjecting the cleaned gases to the action of sulphuric acid in a saturator or absorber, the gases can be freed from ammonia, and can vthen be advantageously cooled for the, separation of a tar acid oil therefrom. This cooling can be elected either indirectly or directly by the introduction of water into the gases. The cooling of the gases by direct contact with water has the advantage that since ammonia is absent from the gases, thel water does not require -subsequent-treament for the recovery of ammonia therefrom. The cooling of the gases for the separation of the tar acid oil maybe, for example, to a. temperature around 25 to 30 C., after which the gases can be passed to an absorber or scrubber for the recovery of coke oven light oils, including benzol, etc.

In carrying out the process of the invention, the hot coke oven gases from the individual ovens may be collected in a common collector main in the ordinary way` and subjected therein to regulated cooling with ammonia liquor, or with ammonia liquor and tar. The cooling should be regulated' so that the gases leaving the collectormain are at a suiciently high temperature so that they can bepassed through a cleaning device` such as an electrical precipitator, at a suiiiciently high temperature to remove a pitch product of comercial properties therefrom, while leaving a considerable amount of the tar acid oil in the vapor state. The cooling of the gases in the collector main will throw down a considerable amount of heavy tar, which may carry with it some of the tar-acids separated from the hot coke oven gases by the local over-cooling of part ot the gases in contact with the ammonia liquor, but the gases as a whole will be maintained at a suiiiciently high temperature on leaving the collector main so that they carry in suspension pitch particles and tar acid oil vapors. By then subjecting the gases to the action of the electrical precipitator, the pitch particles will be separated therefrom iii the form of a pitch of the desired melting point, while the clean gases will contain the tar acid oils in vapor form and can then be passed directly to the ammonia absorber or saturator, and then to a cooler for the separation of tar acid oils.

The pitch separated in the electrical precipitator may contain some water, where ammonia liquor is carried in suspension in the gases entering the precipitator, or where water is condensed by local over-cooling of some of the gases. In such case the pitch can be heated in the bottom of the electrical precipitator to free it from water so that the pitch drawn off from the precipitator will be suitable for use directly. or for shipment. without requiring further treatment. This pitch. therefore` forms one of the valuable directly recovered productsk of the process, being a pitch of regulated melting point as directlv recovered from the hot gases and, if desired. in a water-free condition.

It will be seen that the present invention involves the production or separation from the hot coke oven gases irst of a heavv tar and then ,of a low melting point pitch before the gases are passed through the ammonia absorber. The heavv tar will. moreover. be

separated from the gases before the separa-V tion therefrom of the low melting point pitch. and the heavv tar separated mav be at a lower temperature than the temperature of the pitch. even though the gases from which it is separated are at a higher temperature. When ammonia liquor is employed for cooling the gases'in the collector main. and in the goose-neck through which the gases enter the collector main` the ammonia liquor will come into direct contact with a part of the gases, and will cool such part of the gases so that a heavv tar will be separated therefrom. Part of the gases. however. will not come into contact with the ammonia liquor and willremain at a high temperature. so that the mixture of gases leaving the collector main and passing tothe electrical precipitator may be at a materially higher temperature than that to which part of the gases are subjected in the collector main, although materially lower than that of part of the gases passing through the collector main.

In the electrical precipitator local overcooling is undesirable, since the action desired is the throwing out of the gases of suspended particles of low melting point pitch carried thereby, so as to leave gases free from such pitch constituents for passage to the ammonia absorber. The temperature to which the gases are cooled in the collector main, and at which they pass through the precipitator, can advantageously be regulated by noting the melting point of the pitch separated in the precipitator and' raisingor lowering the temperature of the gases to increase or decrease the melting point of the pitch when it is of too low or too high a melting point.

The composition of coal distillation gases varies somewhat with the particular coal or mixture ot coal beingr coked, the temperature and rate of heating during the coking operation. etc.` but where, for example, it is desired to make a low melting point pitch having a melting point around 105 to 110 F. (or 40.5 C. to 43.5 C.) the particular temperature to be maintained for the gases undergoing treatment can readily be ascertained. lVith certain coke oven gases this temperature was found to be around 110 to 120 C. Such temperatures are sufficiently high not only to give a low melting point pitch suitable for use directly for road treating and other purposes, but to maintain in the gases a considerable amount of tar acid oil vapors so that, after the gases have been passed through the electrical precipitator above the dew point of water, they can be subsequently cooled to separate a tar-acid oil therefrom, which can be directly extracted, for example, With a caustic soda solution to separate the tar acids therefrom.

In my companion case, Serial No. 202,7 36 filed June 30, 1927, I disclosed a process of recovering tar acid oils directly from hot coke oven gases by cleaning the gases at a sufficiently high temperature to leave tar acid oils in the vapor state; then cooling the gases to separate the tar acid oil therefrom, and then passing the gases through the ammonia absorber. The process of the present invention is distinguished from such process, in that it involves subjecting the gases to the action of the acid bath in the saturator or absorber at a sufficient temperature to leave tar acid oils in vapor form, and then subsequently cooling to condense tar acid oils before the gases are subjected to the final scrubbing for the recovery of coal tar light oils.

The process of the present invention is also distinguished from the process of my companion application Serial No. 206,365, led July 16, 1927 in that the present process involves the direct production of a low melting point pitch, suitable, for example, for use for road-treating purposes, while the process of my companion application involves the production ofarelatively high melting point pitch and of a creosote oil directly fromthe gases before they pass through the ammonia absorber. The process of the present invention, like that of my said companion application, involves subjecting the gases leaving the saturator to two successive recovery treatments; first for the recovery of tar acid oils,

- free by adding a small amount of sulphuric and nally for the recovery of coke oven light oils.

The extraction of the tar acids from the tar acid oil can be effected by treatment ofthe 011 with a solution of a phenol-combining substance, such as caustic soda, as more fully described in my companion application Serial treatment with carbon dioxide, for example,

to set free the phenols and to form `s odium carbonate, the last of the phenols being set acid. The phenols thus set free can be sepai rated from the sodium carbonate solution and further distilled or rened to produce commercial products vor fractions therefrom.

In .some cases the tar acid oil may also be rich in naphthalene. In order to prevent separation of naphthalene, the extraction .of the tanacids should be carried out at a temperature su'iciently high to keep the naphthalene in a liquid state. After the extraction of the tar acids from the oils, the naphthalene content will be considerably increased, and, by cooling the neutral oils, naphthalene may be directly separated therefrom in crystalline form, thus enabling naphthalene, as well as tar acids, to be directly recovered at the coke oven plant. l

The invention will be further described in connection with the accompanying drawings,

which are somewhat diagrammatic and conventionalin character, and which illustrate an apparatus embodying the invention and adapted for the practice ofthe process of the invention. p j

In the drawings, Fig. 1 isa plan view showing in a more or less diagrammatic manner apparatus for carrying out this invention;

Fig. 2 is a cross section through the collector main and electrical precipitator of Fig. l

Fig. 3 is a cross sectional elevation of the precipitator shown in Fig. 2; and

Fig. 4 is a diagrammatic view of suitable extraction apparatus.

Referring tothe drawings, 5 indicates a battery of coke ovens in which the individual ovens are connected by uptake pipes and goose-necks 6 to a collector main 7 having center-box 8. Ammonia liquor and tar. can be supplied to the collector main and goosenecks inregulated uantity throu h the spray nozzles 9 and 10 rom a suitab e source 11 by pump 12 through the pipe 13. The amount of ammonia 4liquor and tar thus supplied for cooling purposes is regulated so that the gases leaving the collector main through the pipe 14 pass t ru` the electrical precipitator 15 at a temperature such that a pitch of commercial v value will be separated from the gases, and

such that the gases after leaving the `precipitator will pass through the saturator 17 at a temperature above the dew-point of water. The gases may pass through the .precipitator at a temperature of 110 to 120 C. for example. The tar and ammonia liquor which collect in the'center-box of the collector main can be withdrawn through the pipe 18 intoa decanter 19 from which ammonia liquor will be'withdrawn into the receiver 20 and tar will be collected in the tank 21.

The electrical precipitator used may be of any suitable type. It is arranged preferably closely adjacent to the collector main. The electrical precipitator illustrated is designed especially for use with gases of high temperature. It consists of a shell 22 enclosing a number of tubes 23 supported in heads 24 and 25 within the shell. An inlet 26 near the bottom of the shell communicates with the chamber 27 which ispartially separated from the tube'section by a baiile 28. 'An outlet ,29 permits the escape of gases from the separator. r

A plurality'of electrodes 30, preferably in the'form of metal rods, tubes and are supported from a bus-bar 31 located near the 'upper ends of the tubes.

' The bus-bar 31 extends atboth endsinto casings 32 which enclose insulators 33 upon which the bus-bar is supported. The high tension current lines extend into the casings "32 and connect with the bus-bar 31, thus supplying the necessary current from any suitable source of unidirectional current under high tension. The casing of the separator is grounded or otherwise connected to the source of current to complete the circuit. The casing and tubes form the positive electrode, the electrodes connected to the bus-bar being negative.

The gases carrying heavy tar or pitch 1n the form if globules or fog, togetherwith solid particles such as carbon, etc., enter the electrical precipitator and pass through the tubes, being subjected therein to the electrical discharge which causes them to separate fromthe gases and vapors. The separated liquids, together with the solid particles, run down the inner walls of the tubes into the chamber 27 andcan be withdrawn through a pipe 34 from the bottom of the precipitator. The `gases carrying the condensable vapors escape-through a cross-over extend through the d main 16 and are delivered thereby to the saturator 17. Y,

The saturator illustrated is of the conventional type with a centrifuge 35 and an acid separator 36 to remove entrained acid from the escaping gases. I

From the saturator the ases pass to a condenser 37 which maybe o? any suitable type such as the usual wet condenser, where t e gases are sprayed with water for coolin and removal of the light oil, i. e. the tar acid oil or carbolic oil. After leaving the condenser, the gases may be passed throu h the exhauster 38 to the cooler 37 an thence to scrubber 39 to recover coke oven light oils and from there to suitable storage.

In the drawings, the condenser is illustrated as an ordinary Wet condenser iii which. the gases are s rayed with water through the pipe 40. Tiie condensate from the condenser is drawn off into the decanter 41 from which the condensed oil is collected in the receiver To remove the tar acids from this oil, it is passed through the pipe 43 to extraction apparatus 44 which may comprise a tank having suitable Aagitating means 45 therein. The extraction agent, for example, a 10% solution of caustic soda, can be added in suit able proportions to the tank through an inlet 46 and mingled with thev oil by agitation until the extraction is accom lished. The oil can then be decanted throug pipe 47 and the carbolate solution can' be Withdrawn through an outlet 48 and subjected to any suitable treatment for the separation of the tar acids, such as treatment with carbon dioxide, and the tar acids can then be` refined to produce refined or fractionated products.

The extraction of the tar acid oil with e. g. a caustic soda solution should be carried out at a temperature above that at which the naphthalene crystallizes out, unless any ex cess of naphthalene is first removed from the oil by cooling to a low temperature. After the separation of tar acids, the oil if rich in naphthalene can be cooled to crystallize naphthalene therefrom inI a relatively pure state. Naphthalene, as well as tar acids can thus be directly recovered as a commercial product of the process.

It will thus be seen that the improved process of the invention provides not only for the direct recovery of ammonia from the coke oven gases at a temperature above the `devvpoint of water, so as to avoid condensation of Water during the ammonia absorption, but also for the recovery of a commercial pitch product from the gases prior to the ammonia recovery, and the recovery of both a tar acid oil from which taracids areextracted and also of coke oven light oil after the gases have been freed from ammonia, so that except for the heavy tar separated in the coldirectly recovere 1,sas,eoo

lector main, the products of the proce are commercial products.

I claim:

1. The method of treating hot coal distil-` lation gases, Y. which `comprises cooling the gases to a regulated temperature such that when cleaned with an electrical precipitator, there will be directly'separated therefrom a pitchhaving a melting point of about 105 to 110 F., and a considerable amount of tar acid yoils will be left in the vapor state, cleaning the gases by electrical precipitation subsequently treating the resulting cleaned gases for therecovery of ammonia at a suiiiciently hi h temperature to leave tar acids in vapor orm, treating the resulting ases for the recovery of tar acid oils there rom, and extracting tar kacids from such oils.

2. The method of treating coke oven gases which comprises cooling the same to a regulatedtemperature 110 to 120 C., passing the gases at ,such temperature through an electrical precipitator to se arate therefrom a pitch product suitable or use for road treating purposes, subjecting the resulting cleaned gases to treatment with sulphu'ric acid for the recovery of ammonia therefrom at a temperature above the dew point of Water, coolingthe gases to separate tar acid oils therefrom and extracting tar acids from such oils.,

3. The method of recovering tar acids, which comprises removing from hot coal distillation gases heavier tar constituents and ammonia at a temperature suthciently high to leave a considerable amount of tar acid oils in the vapor state, cooling the resulting cleaned gases to separate tar acid oils therefrom, and extracting tar acids from such oils.

4. The method of recovering tar acids and naphthalene from hot coke oven gases, which comprises removing heavier tar constituents and ammonia from such gases at a tempera ture suiiiciently hi h to leave a considerable amount of tar aci oils and na hthalene in the vapor state, cooling the resu ting cleaned gases to separate tar acid oils containing naphthalene therefrom, extracting such oils to separate tar acids therefrom at a temperature above that of separation of the naphthalene, and subsequently cooling the oils to separate naphthalene therefrom.

5. The method of treating hot coal distillatiori gases which comprises cooling the ases to a regulated temperature, 110 to 120 such that they carry in suspension pitch particles of a melting point adapting them or use for road treating urposes, subjecting the gases at such regu ated temperature to an electrical dischar thereby effecting the separation of such pitch particles therefrom, and thereby obtaining directly from the gases a pitch suitable' for road treating purposes.

6. The method of treating hot coal distillation gases which comprises'cooling the gases to such a. temperature that suspended particles of pitch condensate with a meltin oint of 105 to 110 F. (40.5 to 43.5 C' orm therein, subjecting thewresulting mix-- ture of gases and entrainedpitch particles` to cleamng by veiecting an electrical discharge therein whereby a. pitch product havp lo ing a melting point of 105 to 110 F. is

se rated from the ases.

The method o treating hot coal distillation gases which comprises cooling the gases to v11G-L20" C., cleaning the gases by I' 15 subjecting them to an electrlcal discharge to remove therefrom a pitch suitable for road treating urposes, and subsequently cooling the resu ting gases to-separate therefrom en oil contaimn'g tar acids.

20 1n testimony whereof I aiix my signature.

STUART PARMELEE MILLER. 

